Featured Images not appearing in Facebook

I purchased the "On Demand" theme, which was working beautifully for a while; when I would share on facebook, it would pull the featured image and post to my page. For some reason, in the past week or two, when I try to share, it starts to load and then goes blank and no photo posts.
When I try the 'object debugger' from Facebook I get the following message for "Open Graph Warnings that should be fixed:"

Extraneous Property: Objects of this type do not allow properties named 'twitter:image'.
Extraneous Property: Objects of this type do not allow properties named 'twitter:card'.
Parser Mismatched Metadata: The parser's result for this metadata did not match the input metadata. Likely, this was caused by the data being ordered in an unexpected way, multiple values being given for a property only expecting a single value, or property values for a given property being mismatched. Here are the input property =>content pairs that were not seen in the parsed result: 'twitter:image => http://americanchefinlondon.files.wordpress.com/2012/07/img_2499.jpg, twitter:card => photo'

I can't for the life of me figure out what is wrong and it's killing me because my posts now seem very unprofessional. Is there anyone out there that can please help me? I've been googling the problem for a week and checking the forums but can't find any solutions.